This study will examine how the brain makes involuntary spasms and contractions in patients with focal hand dystonia (FHD). Patients with dystonia have muscle spasms that cause uncontrolled twisting and repetitive movement or abnormal postures. In FHD, only the hand is involved. The study will use functional magnetic resonance imaging (fMRI, see below) to study which areas of the brain are primarily affected in FHD and better understand how brain changes produce dystonia symptoms.